1. Field of the Invention
The present invention relates to an apparatus for controlling the depth of a cable, such as a seismic hydrophone streamer, in water.
2. Description of the Prior Art
Beginning with early attempts to control the depth of submerged seismic cables during exploration, such as a single drogue assembly drawn behind the cable in U.S. Pat. No. 2,465,696, or the spaced weights and floats of U.S. Pat. No. 2,729,300, considerable effort has been expended to accurately control the cable depth at a desired depth.
One approach, as exemplified by U.S. Pat. Nos. 3,375,800 and 3,434,446 (of which applicant is an inventor), and also in U.S. Pat. Nos. 3,412,704; 3,496,526; 3,541,989; and 3,605,674 has used plural apparatus, each mounted in a housing about the seismic cable at spaced positions along the length of the cable. With this approach, the housing surrounding the cable tended to confine undesirable noise in the area of the cable which could be sensed by the sensing geophones or hydrophones in the seismic cable. Further, with these apparatus, the depth controlling diving planes were mounted with the apparatus at the thickest portion thereof, increasing the width or cross-section span of the apparatus. Also, if the cable were over-filled with fluid, undesirable binding between the housing and the cable often occurred.
Other apparatus, such as in U.S. Pat. Nos. 3,372,66; 3,611,975; 3,531,762; and 3,531,761 have included even larger wing structure connected at a single connector to the cable and were comparatively hard to control and unwieldy. Further, the large wing structure frequently snared marine weeds and growth and other submerged objects. Still other apparatus, such as in U.S. Pat. No. 3,434,451 have used two control vehicles, one submerged with the cable, with the other at the water surface subject to wave action and thus generally undesirable.
Finally, other depth control apparatus, such as in U.S. Pat. Nos. 2,709,981; 3,492,962; 3,199,482; 3,260,232; 3,560,912; and 2,945,469 were intended for depth control of specialized structure and not, so far as is known, readily adapted to control the depth of seismic cables.